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drawing filled disk


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#1 giugio   Members   -  Reputation: 215

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Posted 19 October 2012 - 12:54 PM

hello.
I have created a little engine in 2d in opengl for qt.
I Would create a system for create a filled disk and a rectangle(for now) of different color ,positioned at the mouse x,y when i click.
The question is :
1)How i can create the disk? with the sine/cosine and a step angle and for the fill? but is better on the shader(GLSL) or on the cpu ?
2)i wish parametrize the color for ex.
If i create a vbo with the color attribute every time that the color must change i must change the vbo.
Is not better using a uniform var with the color and matrixes for the scale/translate/rotate for the entities?

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#2 Lauris Kaplinski   Members   -  Reputation: 841

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Posted 19 October 2012 - 03:25 PM

1)How i can create the disk? with the sine/cosine and a step angle and for the fill? but is better on the shader(GLSL) or on the cpu ?

As you will have about 100 vertices max, there is no reason to do it in GPU - calculate the positions (via sin/cos) on the CPU and store in VBO

2)i wish parametrize the color for ex.
If i create a vbo with the color attribute every time that the color must change i must change the vbo.
Is not better using a uniform var with the color and matrixes for the scale/translate/rotate for the entities?

You are already at correct path Posted Image
Lauris Kaplinski

First technology demo of my game Shinya is out: http://lauris.kaplinski.com/shinya
Khayyam 3D - a freeware poser and scene builder application: http://khayyam.kaplinski.com/




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